SPECIAL PHYSIOLOGY. 61 



animals (birds) from which this latter physiologist removed 

 the cerebellum, "flying sensations and perceptions remained ; 

 the possibility of executing combined movements likewise 

 persisted, but the co-ordination of movements into movements 

 of regulated and definite locomotion was lost." This has been 

 the view adopted by the majority of physiologists ; and Lus- 

 sana has even gone further, and attributes to the cerebellum 

 the function of the centre of muscular sensibility. However, 

 these functions of locomotion are manifested only when the 

 deeper portions of the cerebellum are injured, whilst super- 

 ficial injuries do not give any result, and leave us without 

 any indications of the functions of the cortical layers of the 

 cerebellum. Moreover Vulpian and Philippeaux have caused 

 no disturbance of locomotion in fishes after ablation of the 

 cerebellum ; let us recall to mind also that physiology of the 

 pinal cord has furnished almost all the elements necessary to 

 explain the reflex mechanism of locomotion ; moreover, Kiiss 

 saw a rabbit whose head he had amputated with dull scissors, 

 thereby hacking the head so as to prevent hemorrhage, jump 

 from the table and run the whole length of the room with a 

 perfectly defined movement of locomotion, and we shall 

 arrive at the conclusion that, in spite of the very numerous 

 solutions that have been offered to explain the physiology of 

 the cerebellum, we still possess no precise notion of the func- 

 tions of this nervous centre. 



The corpora striata and optic thalami are inexcitable, as 

 well as the gray axis of the spinal cord, and all the gray 

 centres ; we cannot then arrive at a knowledge of their func- 

 tions except by their destruction in animals, or by the study 

 of the clinical phenomena which follow their alteration, either 

 by the presence of a tumor or by a hemorrhage. In these 

 cases no lesions of general sensibility have been proved, nor 

 of any special sensibility, and we must admit that the optic 

 thalami, in spite of their name, have no more concern with 

 vision than the corpora striata have with the sense of olfac- 

 tion. Lesions of these centres produce only paralyses (par- 

 alysis on the opposite side, as we have seen a propos to the 

 conductors in the spinal cord), and we may consider the cor- 

 pora striata and optic thalami as grand excito-motory centres, 

 but without assigning to the former the movements of the 

 posterior extremities, and to the latter those of the anterior 

 extremities. 



The corpus callosum (trabs cerebri), and the different com- 

 missures between the cerebral hemispheres taught in anatomy, 



